Metallurgical slag reaction



W. ROHN MBTALLURGICAL SLAG REACTION Oct. 26, 1937.

Filed Dec. 5, 1935 Patented Oct. 26, 1937 UNITED STATES METALLUBGICAL SLAG BEACTION Wilhelm Bohn, Banan-on-the-Mal, Germany, asslnor to Heraes-Vacuumschmele A. G.,

Banan-on-the-Main,

company I i Application December 5, 1933, Serial No.

In Germany Germany, a German December 8, 1932 3Clalm.

This application is a oontinuation in part of nU. S. Patent No. 1,983,242, filed August 15, 1

The invention relates to a process i'or accelerat- 8 ing metallurgical slag, reactions in inductively heated electric melting iumaces.

The increasing introduction o! inductively heated electrlc metallurgical melting iurnaces has shownthat the motion in the bath occurring in such neting fumaces has a strong accelerating and assisting action on a. number of known metal-' lurgical processes including, inter alla, the reduction of the carbon, sulphur and phosphorus content. 'inis knowledge has assisted materially in 1 the increasing introduction into metalurgical practice oi' the so-called high irequency furnace.

In the accomp yi drawing, Fle'. 1 is a vertical section illustrating one feature oi'the present invention; Fig. 2 is a plan' view of the same with markings thereon' further illustrating the same; Fig. 3 is a panorama view o! the same; Flg. 4 iilustrates diically one feature of the electric i'urnace .utilized in the practice of the present invention; Fig. 5 is a. perspective view o! another feature; and Fig. 6 is a sectional view along plane 3-4 oi' Fig. 5.

Re! to the drawing, in all figures a is the hea-th, h is the molten metal bath, c--c are the induction coils for energizing the bath, y is the yoke and p is the etic pole piece. Arrows q indicate the circulatory motions' imparted to the bath by* reason of the specific iurnace construction and ti indicates the slag with which it is desired iso-recet the bath b in accordance with the present intention.

In a high frequency furnace known per se the molten metal rises in the centre oi the iurnace, flows outwardly towards the periphery and there flowsdownwnrdly and laminarliy along the lining.

40 The slag provided on the surface of the bath tor exertins metallurgical reactions is accordingly driven to the e oi the !used metal and collects for the creator part at the lining oi the furnace. Insofar as the slag is able to react with the lining this collection of the slag leads to a comparatively rapid eroslon of the lining at the points at which the slag mmm-into contact therewith.

In itself it would be desirable to make provision for the slag to be held as tar as possible away !mm the walls o! the furnace, i. e. from the lining; further it would be desirable to make the motion in the bath, which'in the induction furnaees hitherto known is essentially laminar, so violmt and so turbulent that the bath does not merely move continuously past the slag lying quietly on its surface but that the slag is stil-red into the bath as an emulsion. y

The features which are indicated above as being desirableare attained it the axes oi the -induction coils are not arrangedverticaily and 'concentrically with respect to the bath as hitherto customary in high frequency furnaces but are dis-. posed primarily radially and horizontally. A further improvement is attained ii the metallurgical meltng fumace heated by induction is supplied not 'with single or'two phase alternating current but with three-phase current. The mode of operation orsuch arrangements is 2 and 3. u

In Fig. 1 the induction coils c, c which are diagrammaticaliy shown in Fig. 4 have nearly horizontally and radially directed axes. In consequence o! the action of the rotating field the entire bath is caused to rotate about a vertical axis. This hasthe eifect that the bath is at a 'higher level at the periphery than at the centre so that in consequence the slag d present on the surface oi' the bath coliects primarily at the centre of the bath and thus is kept irom a too intimate contact with the lining.

In Fig. 2, which again shows a plain view of the surface oi' the bath in a furnace according to the invention, the points at which the bath moves upwardly from below are shown by solid circles e whereas the points at which the bath flows downwardly are indicated by open circles f. This illustration is based on a furnace with three poles. In Fig. 4, which is drawn on a smaller scale than Figs. 1 and 2, g is a trlangular yoke y with the three 'poles p', p p these elements of the fur- 5 hace not being shown in'Figs. 1 and 2. It is seen that in consequence of the arrangement of the induction coils, c, with nearly horizontal radial axes there are rising and falling motions directly adjacent one another in the horizontaliy rotating bath'about a plurality of horizontal axes equal to the number of coils c, which gives rise to a strong turbulence of the horizontally rotating flow of the bath and in consequence the'bath does not v indicated in Figs.1, i

widinas and current input substantially as described in my Patent No. 1,983,242.

The panorama view o! Fig. 3 is shown on a somewhat smaller scale than Flg. 2 and the motions in the bath are again indicated by arrows q.

The idea of turnishing induction turnaces with `coils the axes o! which' are arranged radially and predominately horizontally is not novel. When in spite o! this the above described phenomena and motions in the bath have not hitherto been disclosed and utilized, this may perhaps be attributed principally to the fact that such furnaces although proposed on paper many times have not yet been utilized in practical operationat all. The study of the phenomena referred to in a three-pole three phase furnace constructed as described and claimed in my prior Patent 1,983,-

242, Figs. 7 and 8 of the drawings of said patent' being reproduced as Flgs. 5 and 6 of the present application, containing about 1600 kilos has shown that the difference in level between the centre oi' the bath and the'edge of the bath can amount to 10 to 12 cm. and has the eflect that the slag accumulates principally in the censre oi the bath. Along the three lines i in Fig. 2, at which upwardly directed and downwardly directed motions are immediately adjacent one another in the bath there are diflerences in level o! from 4 to 6 cm. so that at these points there is the appearance oi a standing breaker. Quantities oi' slag ot'from to kilos are in this way drawn unde; the surface oi' the bath so that the entire surface of the bath exhibits a metallic 'appearance and there are no accumulaticns of slag on the surface at all. The extremely violent motion of the bath, the intensity o! which has not been attained in any induction furnace hitherto constructed, renders it possible to reduce the carbon content of a charge of 1600 kilos from 1.0 to 002% o! carbon within 30 to 50 minutes in the furnace described, or to reduce the phosphorus dizing constituents heretoiore used in the art to form a basic oxidizing slag.

The furnace structure illustrated in Figs. 5 and 6 being. fully described in my above identified patent need not be furthe described herein beyond identiiying the various elements thereo! to coni'orm with the above description of the present invention.

From the above description it is apparent that many modiflcations and adaptions may be made therein without departing essentially from the nature and scope as may be included within the following claims:

I claim:

1. The method of puriiying molten metal bathe with a reacting slag which comprises emulsifying the slag within the molten metal by rotatively strring the bath about a plurality ot radia axes lying in substantially horizontal planes as well as e -rotatively stirring the bath horizontally about a center vertical axis by means o! induced electrlc currents.

2. In the method of claim 1, ,regulating the intensity o! said currents to maintain the desired reacting temperature in the bath and the desired degree of'emulsiflcation o! the slag in the molten metal.

3. The method of claim 1 in which the molten metal bath is comprised of pig iron and the reacting slag is an oxidizing slag adapted-to remove carbon, phosphorus and suliur from the said pis iron.

WILEELM ROHN. 

